These studies utilize participants in the Baltimore Longitudinal Study of Aging. Plasma samples were obtained during an oral glucose tolerance test and then measured in duplicate by double-antibody radioimmunoassay. Cross- sectional and longitudinal analyses are employed to gain insight into the complex inter-relationships among post-load and fasting plasma insulin levels and age, sex, obesity, fat distribution, lipids, and blood pressure. Due to the increased morbidity associated with hyperlipidemia, hypertension, hyperinsulinmenia and obesity, the projects are directed toward attempting to determine the causal order, if one exists, among these metabolic variables as well as the roles of sex and aging. From the cross- sectional findings of this project it can be concluded that: 1) Correlations of blood pressure and plasma insulin levels after adjustment for age, obesity, and fat distribution were entirely non- significant; 2) The sex differences in fasting and postload insulin levels are explained by differences in body habitus but that insulin levels decline with age per se.